From 0a0559824a4923fc5fbd77c18c2654fb15a14a2b Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Motiejus=20Jak=C5=A1tys?= <motiejus@jakstys.lt>
Date: Tue, 15 Mar 2022 07:47:52 +0200
Subject: [PATCH] Bdz index helper

---
 src/sections.zig | 68 ++++++++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 66 insertions(+), 2 deletions(-)

diff --git a/src/sections.zig b/src/sections.zig
index 79db780..f1b8ae4 100644
--- a/src/sections.zig
+++ b/src/sections.zig
@@ -340,6 +340,29 @@ pub fn groupsSection(
     };
 }
 
+// creates a bdz index using packed_mphf. buf[bdz_search(key)] = index(keys, key)
+pub fn bdzIdx(
+    comptime T: type,
+    allocator: Allocator,
+    packed_mphf: []const u8,
+    keys: []const T,
+) error{OutOfMemory}![]const u32 {
+    const search_fn = comptime blk: {
+        switch (T) {
+            u32 => break :blk bdz.search_u32,
+            []const u8 => break :blk bdz.search,
+            else => unreachable,
+        }
+    };
+    std.debug.assert(keys.len <= math.maxInt(u32));
+    var result = try allocator.alloc(u32, keys.len);
+    for (keys) |key, i| {
+        const hash = search_fn(packed_mphf, key);
+        result[hash] = @intCast(u32, i);
+    }
+    return result;
+}
+
 // cmpUser compares two users for sorting. By username's utf8 codepoints, ascending.
 fn cmpUser(_: void, a: User, b: User) bool {
     var utf8_a = (unicode.Utf8View.init(a.name) catch unreachable).iterator();
@@ -411,6 +434,19 @@ pub const AllSections = struct {
             mem.sliceAsBytes(shell_sections.blob.constSlice()),
         );
 
+        var idx_gid2group = try bdzIdx(
+            u32,
+            allocator,
+            bdz_gid,
+            corpus.groupsm.items(.gid),
+        );
+        var idx_groupname2group = try bdzIdx(
+            []const u8,
+            allocator,
+            bdz_gid,
+            corpus.groupsm.items(.name),
+        );
+
         return AllSections{
             .allocator = allocator,
             .bdz_gid = bdz_gid,
@@ -423,8 +459,8 @@ pub const AllSections = struct {
             .users = users,
             .group_members = group_members,
             .groups = groups,
-            .idx_gid2group = undefined,
-            .idx_groupname2group = undefined,
+            .idx_gid2group = idx_gid2group,
+            .idx_groupname2group = idx_groupname2group,
             .idx_uid2user = undefined,
             .idx_name2user = undefined,
         };
@@ -440,6 +476,8 @@ pub const AllSections = struct {
         self.users.deinit(self.allocator);
         self.group_members.deinit(self.allocator);
         self.groups.deinit(self.allocator);
+        self.allocator.free(self.idx_gid2group);
+        self.allocator.free(self.idx_groupname2group);
         self.* = undefined;
     }
 };
@@ -649,3 +687,29 @@ test "users compare function" {
     try testing.expect(cmpUser({}, b, bb));
     try testing.expect(!cmpUser({}, bb, b));
 }
+
+test "bdzIdx" {
+    const allocator = testing.allocator;
+    const k_u32 = [_]u32{ 42, 1, 2, 3 };
+    const k_str = [_][]const u8{ "42", "1", "2", "3" };
+    const mphf_str = try cmph.packStr(allocator, k_str[0..]);
+    const mphf_u32 = try cmph.packU32(allocator, k_u32[0..]);
+    defer allocator.free(mphf_str);
+    defer allocator.free(mphf_u32);
+
+    {
+        var result = try bdzIdx(u32, allocator, mphf_u32, k_u32[0..]);
+        defer allocator.free(result);
+        var used = [_]bool{false} ** 4;
+        for (result) |elem| used[result[elem]] = true;
+        for (used) |item| try testing.expect(item);
+    }
+
+    {
+        var result = try bdzIdx([]const u8, allocator, mphf_str, k_str[0..]);
+        defer allocator.free(result);
+        var used = [_]bool{false} ** 4;
+        for (result) |elem| used[result[elem]] = true;
+        for (used) |item| try testing.expect(item);
+    }
+}